1. Field of the Invention
The present invention relates to a solenoid valve for a brake system, and more particularly, to a solenoid valve for a brake system having an improved assembly configuration of constituent elements thereof.
2. Description of the Related Art
Generally, a vehicular hydraulic brake slows or stops a vehicle by applying hydraulic pressure to a master cylinder according to operation of a brake pedal. In this case, when a greater braking force than a stoppage frictional force between a tire and a road surface is applied to the tire, there occurs a tire slippage phenomenon on the road surface.
However, since a coefficient of kinetic friction is less than a coefficient of static friction, it is necessary to prevent the tire slippage phenomenon in order to achieve optimal braking. In addition, it is necessary to prevent a steering lock phenomenon that prevents steering during operation of the brake.
An anti-lock brake system serves to prevent the above-described phenomenon by controlling hydraulic pressure applied to a master cylinder. The anti-lock brake system basically includes a plurality of solenoid valves, an ECU to control the solenoid valves, an accumulator, and a hydraulic pump.
The solenoid valves are classified into normal open type solenoid valves, which are arranged at the upstream side of a hydraulic brake and are normally kept in an opened state, and normal close type solenoid valves which are arranged at the downstream side of the hydraulic brake and are normally kept in a closed state.
FIG. 1 is a sectional view illustrating a configuration of a conventional normal close type solenoid valve. As shown in FIG. 1, the conventional normal close type solenoid valve (hereinafter, referred to as a “solenoid valve”) is installed in a modulator block 1 to enhance responsiveness. The modulator block 1 is formed with a bore 2 by cutting for installation of the solenoid valve.
A first valve block 3 is fitted in a hollow first valve block 3. A cylindrical guide sleeve 4 is coupled to one end of the first valve block 3, and an armature 5 is disposed in the guide sleeve 4. Also, a valve core 6 is fitted into an open end of the guide sleeve 4 and serves to drive the armature 5.
A plunger 5a is integrally provided at one end of the armature 5, and serves to open or close a flow-hole 7a of a valve seat 7 according to sliding movement of the armature 5. A return spring 5b is inserted between the other end of the armature 5 and the valve core 6. The return spring 5b elastically supports the armature 5 such that the armature 5 normally keeps the flow-hole 7a in a closed state.
An O-ring 8 is fitted around the first valve block 3 to seal a gap between an entrance-side and an exit-side of the solenoid valve. An orifice plate 9 is coupled to a lower end of the first valve block 3. The orifice plate 9 has an orifice 9a to regulate a flow rate of fluid to be discharged from the solenoid valve.
In addition, an exciting coil (not shown) is installed around the guide sleeve 4 and the valve core 6, to cause sliding movement of the armature 5.
In operation of the above-described solenoid valve, when power is applied to the exciting coil, a magnetic force is generated between the valve core 6 and the armature 5. As the armature 5 is moved toward the valve core 6 by the magnetic force, the flow-hole 7a of the valve seat 7 is opened. On the other hand, since no magnetic force is exerted when no power is applied to the exciting coil, the armature 5 is returned to an original position thereof by an elastic force of the return spring 5b, closing the flow-hole 7a. 
As described above, the conventional solenoid valve is constituted such that constituent elements thereof are arranged about the first valve block 3, and thus, the first valve block 3 must have installation spaces for the valve seat 7, O-ring 8 and orifice plate 9 and inlet and outlet holes 3a and 3b for fluid-flow. Therefore, the first valve block 3 has problems of a large overall size and complicated configuration. The complicated configuration of the first valve block 3 inevitably entails a complex manufacturing process, and results in deterioration of product competitiveness due to an increased production price of the valve.